Guidewire filter and methods of use

ABSTRACT

A filter system for temporary placement of a filter in an artery or vein is disclosed. The filter system includes a guidewire that is first positioned across a lesion within a vessel. The guidewire may include a distal stop. A slideable filter is then advanced along the guidewire using an advancing mechanism, typically an elongate member slideable over the guidewire and contacting the filter. A capture sheath may be disposed about the filter during advancement. Once the filter is positioned downstream of the lesion, the capture sheath is withdrawn, allowing the filter to expand. Further distal advancement of the filter is prohibited by the stop. After expansion of the filter, the capture sheath and the advancing mechanism are withdrawn from the region of interest, and removed from the patient&#39;s vessel. The filter may then be retrieved using a capture sheath or exchanged for a second filter after removing the first filter.

RELATED APPLICATIONS

This is a continuation of U.S. application Ser. No. 11/198,915, filedAug. 5, 2005 which in turn is a continuation of U.S. application Ser.No. 10/077,496, filed Feb. 15, 2002, which in turn is a continuation ofU.S. application Ser. No. 09/560,360, filed Apr. 28, 2000, now U.S. Pat.No. 6,371,971, which in turn is a continuation of U.S. application Ser.No. 09/440,204, filed Nov. 15, 1999, which is expressly incorporatedherein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to devices and methods forproviding temporary placement of a filter in a blood vessel. Moreparticularly, the invention provides a filter cartridge system forentrapment of embolic material in an artery or vein during anendovascular procedure. The system permits the replacement of the filtercartridge without requiring the removal of the guidewire during theendovascular procedure.

BACKGROUND OF THE INVENTION

Treatment of thrombotic or atherosclerotic lesions in blood vesselsusing an endovascular approach has recently proven to be an effectiveand reliable alternative to surgical intervention in selected patients.For example, directional atherectomy and percutaneous translumenalcoronary angioplasty (PTCA) with or without stent deployment are usefulin treating patients with coronary occlusion. Atherectomy physicallyremoves plaque by cutting, pulverizing, or shaving in atheroscleroticarteries using a catheter-deliverable endarterectomy device. Angioplastyenlarges the diameter of a stenotic vessel by exerting mechanical forceon the vascular walls. In addition to using angioplasty, stenting,and/or atherectomy on the coronary vasculature, these endovasculartechniques have also proven useful in treating other vascular lesionsin, for example, carotid artery stenosis, peripheral arterial occlusivedisease (especially the aorta, the iliac artery, and the femoralartery), renal artery stenosis caused by atherosclerosis orfibromuscular disease, superior vena cava syndrome, and occlusive iliacvein thrombosis resistant to thrombolysis.

It is well recognized-that one of the complications associated withendovascular techniques is the dislodgment of embolic materialsgenerated during manipulation of the vessel, thereby causing occlusionof the narrower vessels downstream and ischemia or infarct of the organthat the vessel supplies. In 1995, Waksman et al. disclosed that distalembolization is common after directional atherectomy in coronaryarteries and saphenous vein grafts. See Waksman et al., American HeartJournal 129(3): 4305 (1995), (this and all other references cited hereinare expressly incorporated by reference as if fully set forth in theirentirety herein). This study found that distal embolization occurs in28% (31 out of 111) of the patients undergoing atherectomy. In January1999, Jordan, Jr. et al. disclosed that treatment of carotid stenosisusing percutaneous angioplasty with stenting is associated with morethan eight times the rate of microemboli seen using carotidendarterectomy. See Jordan, Jr. et al. Cardiovascular Surgery 7(1): 33-8(1999), incorporated herein by reference. Microemboli, as detected bytranscranial Doppler monitoring in this study, have been shown to be apotential cause of stroke. The embolic materials include calcium,intimal debris, atheromatous plaque, thrombi, and/or air. There are anumber of devices designed to provide blood filtering for entrapment ofvascular emboli. The vast majority of these devices are designed forpermanent placement in veins to prevent pulmonary embolism. A temporaryvenous filter device is disclosed in Bajaj, U.S. Pat. No. 5,053,008,incorporated herein by reference. The Bajaj device is an intracardiaccatheter for temporary placement in the pulmonary trunk of a patientpredisposed to pulmonary embolism due to, e.g., hip surgery, majortrauma, major abdominal or pelvic surgery, or inmmobilization. The Bajajdevice includes an umbrella made from meshwork that traps venous embolibefore they reach the lungs. This device is designed for venousfiltration and is not suitable for arterial use because of thehemodynamic differences between arteries and veins.

There are very few intravascular devices designed for arterial use.Arteries are much more flexible and elastic than veins and, in thearteries, blood flow is pulsatile with large pressure variations betweensystolic and diastolic flow. These pressure variations cause the arterywails to expand and contract. Blood flow rates in the arteries vary fromabout 0.1 to 5 L/min. Ginsburg, U.S. Pat. No. 4,873,978, discloses anarterial filtering system, which includes a catheter with a strainerdevice at its distal end. This device is inserted into the vesseldownstream from the treatment site and, after treatment, the strainer iscollapsed around the entrapped emboli and removed from the body. TheGinsburg device, however, is integral with the catheter, unlike thedevices described later herein. Ing. Walter Hengst GmbH & Co, GermanPatent DE 34 17 738, discloses another arterial filter having a foldinglinkage system that converts the filter from the collapsed to theexpanded state. Filters mounted to the distal end of guidewires havebeen proposed for intravascular blood filtration. A majority of thesedevices include a filter that is attached to a guidewire and ismechanically actuated via struts or a pre-shaped basket that deploys inthe vessel. These filters are typically mesh “parachutes” that areattached to the shaft of the wire at the distal end and to wire strutsthat extend outward in a radial direction at their proximal end. Theradial struts open the proximal end of the filter to the wall of thevessel. Blood flowing through the vessel is forced through the meshthereby capturing embolic material in the filter.

Gilson et al., International Publication No. WO 99/23976 describes aguidewire with a filter slideably mounted thereon. Although the filteris not fixed to the guidewire at a single point, the filter is limitedin its range of movement by two stops at the distal end of theguidewire, the stops being relatively closely spaced. Thus, unlike thepresent invention, in Gilson et al. the filter cannot be removed unlessthe entire guidewire is removed.

The useful in vivo time of a guidewire filter will vary, depending uponthe type of procedure, the patient, and the blood flow. These factorsmay contribute to relatively short use time because of, for example,blood coagulation or excessive emboli clogging the filter mesh. Becausefor existing devices, the guidewire and the filter are integrated intoone inseparable device, changing the filter after its useful in vivodeployment time has been completed requires the removal and replacementof the guidewire. This change requires time consuming and costlyfluoroscopic guidance to reposition the new guidewire and filter.

There is a need in the art for a device that will not require removaland replacement of the guidewire should the in vivo useful life of ablood filter be exceeded. The present invention addresses that need byproviding a blood cartridge filter that may be used and replaced withoutrequiring the removal of the guidewire.

SUMMARY OF THE INVENTION

The present invention provides devices and methods for directing a bloodfilter into position using a guidewire wherein the blood filter may bedeployed and replaced independently of the guidewire. More specifically,a guidewire cartridge filter system is disclosed for capturing embolicmaterial generated during a surgical procedure within a region ofinterest in an artery or vein.

In accordance with the present invention, the cartridge filter systemcomprises an elongate member that acts as an advancing mechanism, e.g.,a push wire or sheath, having a distal region attached to a filter,e.g., a parachute, basket, or scroll filter. In certain embodiments, thefilter may be releasably attached to the elongate member through aninterlock, which may comprise, for example, a mechanical interlock orelectromechanical interlock. The filter may comprise an expansion frameand a filter material, typically a filter mesh, attached to theexpansion frame. The cartridge filter system includes means for engagingthe guidewire, such as a wire guide that slideably engages a guidewire.The wire guide may be attached to either or both of the elongate memberand the filter. In certain embodiments, the wire guide comprises a ringhaving an aperture adapted to receive the guidewire. In certain otherembodiments, the wire guide comprises a body portion of the elongatemember having a longitudinally extending groove adapted to slideablyengage the guidewire. The body portion may thus have a C-shaped crosssection. Because the wire guide slideably engages the guidewire, thefilter may be directed into place by the guidewire, but deployed andretracted independently of the guidewire. The filter can be placed in acollapsed condition to facilitate entry into a vessel and an expandedcondition to capture embolic material in the vessel. As used therein,“advancing mechanism” denotes any elongate member or structure suitablefor advancing the filter into position within a vessel while engagingthe guidewire through the wire guide. The elongate member could thus beeither a wire or a catheter wherein the lumen of the catheter serves asthe wire guide. In one embodiment, the elongate member comprises asheath wherein the lumen of the sheath serves as the wire guide.

Filters suitable for use within the filter system of the presentinvention are described, for example, in U.S. Pat. No. 5,910,154,incorporated herein by reference in its entirety. In one embodiment, thefilter is biased to automatically open radially within a blood vessel.In such filters, the expansion frame may comprise a plurality of strutsor arms attached to and extending distally from a distal end of theelongate member. The struts are connected to each other at each end andhave an intermediate region that is biased to expand radially. Filtermesh is attached typically between the intermediate region such as themidpoint and the distal ends of the struts, thereby defining asubstantially hemispherical or conical shaped filter assembly. Inembodiments of the invention wherein the elongate member comprises asheath, a filter biased to automatically open radially may be releasablycarried in its collapsed condition within the sheath wherein amechanical interlock between elongate member and the filter is formed bythe friction between the filter and the lumenal wall of the sheath.

Other filters suitable for the present invention are not biased toautomatically open radially within a blood vessel. In such filters, theelongate member may comprise a heath containing an inner wire, and theexpansion frame includes a plurality of struts attached to the distalend of the sheath. The struts extend distally from the sheath and attachto the distal end of the inner wire that is exposed distally beyond thesheath. At an intermediate region, the struts are notched or otherwisebiased to fold out radially. Filter mesh is attached to the strutsbetween the intermediate region and the distal end of the inner wire.With the sheath fixed, the inner wire is proximally displaced,compressing the struts and causing them to bend or buckle at theintermediate region and move radially outwardly, expanding the filtermesh across the blood vessel. As used herein, “inner wire” means anystructure suitable to be slideably disposed within the sheath and stiffenough to compress the struts as the inner wire is proximally displacedwith respect to the sheath. The inner wire may thus comprise an innersheath within which the guidewire is slideably disposed.

In certain other embodiments, the filter may comprise a fluid operatedfilter wherein the expansion frame includes a balloon that inflates toexpand the filter into an enlarged condition for use. The constructionand use of expansion frames and associated filter mesh have beenthoroughly discussed in earlier applications including Barbut et al.,U.S. application Ser. No. 08/533,137, filed Nov. 7, 1995, Barbut et al.,U.S. application Ser. No. 08/580,223, filed Dec. 28, 1995, Barbut etal., U.S. application Ser. No. 08/584,759, filed Jan. 9, 1996, Barbut etal., U.S. Pat. No. 5,769,816, Barbut et al., U.S. application Ser. No.08/645,762, filed May 14, 1996, and Barbut et al., U.S. Pat. No.5,662,671, and the contents of each of these prior applications areexpressly incorporated herein by reference.

The methods of the present invention include prevention of distalembolization during an endovascular procedure to remove emboli and/orforeign bodies such as gas bubbles from blood vessels. The vesselsinclude the coronary artery, aorta, common carotid artery, external andinternal carotid arteries, brachiocephalic trunk, middle cerebralartery, basilar artery, subclavian artery, brachial artery, axillaryartery, iliac artery, renal artery, femoral artery, popliteal artery,celiac artery, superior mesenteric artery, inferior mesenteric artery,anterior tibial artery, posterior tibial artery, and all other arteriescarrying oxygenated blood. Suitable venous vessels include the superiorvena cava, inferior vena cava, external and internal jugular veins,brachiocephalic vein, pulmonary artery, subclavian vein, brachial vein,axillary vein, iliac vein, renal vein, femoral vein, profunda femorisvein, great saphenous vein, portal vein, splenic vein, hepatic vein, andazygous vein.

In a method of using the cartridge filter system, the distal end of theguidewire is inserted through an artery or vein and advanced into orbeyond a region of interest, typically a stenotic lesion caused bybuildup of atherosclerotic plaque and/or thrombi. The guidewire may beinserted percutaneously, laparoscopically, or through an open surgicalincision. In a collapsed condition, the filter and the elongate memberare advanced over the guidewire, having the wire guide of the filtercartridge system engaging the guidewire. In one embodiment, the wireguide engages the elongate member at a single discrete location in amonorail fashion such as through a ring structure. If the wire guideincludes a body portion of the elongate member having a longitudinallyextending groove adapted to slideably engage the guidewire, the bodyportion engages the guidewire in an over-the-wire fashion wherein theguidewire is slideably disposed within the groove of the body portion.Alternatively, the elongate member may comprise a sheath wherein theguidewire is slideably disposed within the lumen of the sheath in anover-the-wire fashion such that the lumen serves as the wire guide.Regardless of whether the wire guide engages the guidewire in a monorailor an over-the-wire fashion, the filter is then expanded downstream ofthe vascular occlusion. If the wire guide engages the guidewire in anover-the-wire fashion, the elongate member may be left in the vesselduring the in vivo deployment time of the filter because the elongatemember and the guidewire are then integrated into a single unit,limiting the interference with further deployment of therapy devices inthe vessel. If, however, the wire guide engages the guidewire in amonorail fashion, the elongate member is preferably removed from thefilter during the in vivo deployment time of the filter to prevent aclinician from having to contend with the independent movement of boththe guidewire and the elongate member during the surgical procedure.Preferably, in such embodiments, the elongate member releasably attachesto the filter through a mechanical interlock. After deploying thefilter, the mechanical interlock is released to allow the removal of theelongate member.

Should the in vivo deployment time of the filter be exceeded, the usedfilter is retracted from the body and the guidewire. If the filter andelongate member were separated by releasing an interlock, the wire guideon the elongate member must be engaged with the guidewire so that theelongate member may be displaced distally on the guidewire towards theused filter. The interlock would then be re-engaged to connect theelongate member and the used filter together whereupon the elongatemember may be retracted to remove the used filter. If the elongatemember and the used filter were permanently attached, the elongatemember may simply be retracted to remove the used filter. An additionalfilter and elongate member may then be advanced over the guidewire asdescribed herein. Because the present invention allows the removal andreplacement of filters without requiring the removal of the guidewire,the filter system may be denoted a “cartridge filter” system in that thefilter is akin to, for example, a printer cartridge, readily replaceablewithin the printer. After the stenotic lesion is removed or otherwisetreated and an adequate lumenal diameter is established, the filter iscollapsed and removed, together with the captured embolic debris, fromthe vessel by withdrawing another elongate member used for retrieval.Alternatively, the filter could be removed by withdrawing the guidewireto remove the entire filter system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A depicts an embodiment of an elongate member having a filter in acollapsed condition according to the present invention.

FIG. 1B depicts the elongate member of FIG. 1A having the filter in anexpanded condition.

FIG. 1C depicts a cross-sectional view through section line C-C of theelongate member depicted in FIG. 1B.

FIG. 1D depicts the elongate member of FIG. 1C having a guidewirereceived through the wire guide.

FIG. 2A depicts an embodiment of a distal end of the guidewire.

FIG. 2B depicts an alternative embodiment of the distal end of theguidewire.

FIG. 2C depicts another alternative embodiment of the distal end of theguidewire.

FIG. 3A depicts another embodiment of the filter shaped as a parachute.

FIG. 3B depicts another embodiment of the filter shaped as an eggbeater.

FIG. 4A depicts a guidewire inserted across a vascular occlusion.

FIG. 4B depicts a monorail cartridge filter system being deployed acrossa vascular occlusion.

FIG. 4C depicts a monorail cartridge filter system wherein themechanical interlock connecting the elongate member and the filter hasbeen released.

FIG. 4D depicts an over-the-wire cartridge filter system deployed acrossa vascular occlusion.

FIG. 5A depicts a cartridge filter system wherein the system operate aseither an over-the-wire or a monorail system

FIG. 5B depicts a cross-sectional view through section line B-B of theelongate member depicted in FIG. 5A.

FIG. 6 depicts a cartridge filter system wherein the elongate membercomprises an inner sleeve and wherein the system further includes acapture sheath.

FIG. 7A depicts a guidewire with a distal stop positioned across avascular lesion.

FIG. 7B depicts a slideable filter, an advancing mechanism, and acapture sheath disposed over the guidewire of FIG. 7A.

FIG. 7C depicts the capture sheath crossing the lesion with a filterexpanded downstream.

FIG. 7D depicts the guidewire and slideable filter after removal of thecapture sheath and advancing mechanism.

FIG. 8 depicts an advancing mechanism connected to a slideable filterthrough a flush contact.

FIG. 9A depicts an advancing mechanism connected to a slideable filterthrough pivoting claws.

FIG. 9B depicts the opening of the pivoting claws of FIG. 9A.

FIG. 10A depicts an advancing mechanism connected to a slideable filterthrough a threaded interlock.

FIG. 10B depicts the opening of the threaded interlock of FIG. 10A.

FIG. 11A depicts the slideable filter connected to an advancingmechanism through a mechanical interlock.

FIG. 11B depicts the assembly of FIG. 11A after removal of a capturesheath.

FIG. 11C depicts the assembly of FIG. 11B after rotation of themechanical interlock.

FIG. 11D depicts the assembly of FIG. 11C after removal of the sheathand advancing mechanism.

FIG. 12A depicts an actuatable stop comprising off-center tubes disposedalong a guidewire.

FIG. 12B depicts a distal view of the stop of FIG. 12A.

FIG. 12C depicts insertion of a slideable filter and the stop of FIG.12A into a vessel.

FIG. 12D depicts the slideable filter and stop of FIG. 12C after removalof the capture sleeve.

FIG. 12E depicts the slideable filter and stop of FIG. 12C beforeadvancement of the alignment sheath.

FIG. 13A depicts another embodiment of an actuatable stop having aslideable filter bearing proximally against the stop.

FIG. 13B depicts a capture sheath disposed about and aligning theactuatable stop and filter of FIG. 13A.

FIG. 13C depicts the filter withdrawn proximally over the actuatablestop of FIG. 13B.

FIG. 14A depicts another embodiment of an actuatable stop comprising aslip stop.

FIG. 14B depicts a capture sheath disposed about and aligning theactuatable stop and filter of FIG. 14A.

FIG. 15A depicts a guidewire having a single distal stop.

FIG. 15B depicts a guidewire having proximal and distal stops, whereinthe stops are pivoting barbs.

FIG. 15C depicts a guidewire having a distal stop and two proximalstops, wherein the proximal stops comprise pivoting cleats.

FIG. 15D depicts a capture sheath disposed about and aligning the cleatswith a filter.

FIG. 15E depicts another embodiment of a capture sheath disposed aboutand aligning the cleats with a filter.

FIG. 16A depicts an open carriage filter structure.

FIG. 16B depicts a continuous carriage filter structure.

DETAILED DESCRIPTION

In a first embodiment, a cartridge filter system for temporary placementin a vessel, either an artery or vein, is provided as depicted in FIGS.1A, 1B, 1C, and 1D. The filter system includes an elongate member 10having a proximal end, distal region 11, and expandable filter 20mounted at the distal region. The filter 20 comprises expansion frame 22and mesh 25 that is welded, adhesive bonded, or otherwise disposed aboutstruts 28 of the expansion frame. Alternatively, the filter comprises amembrane extending from a proximal end to a distal end and having anexpandable intermediate region. the proximal end includes segments thatextend to the intermediate region and that have gaps or windows inbetween to allow blood to flow inside the structure. the distal end is acontinuous membrane having holes drilled therein to create a filtermembrane. Anticoagulants, such as heparin and heparinoids, may beapplied to the mesh 25 to reduce thrombi formation. The filter 20 can becollapsed as shown in FIG. 1A to facilitate insertion into a vessel, andthereafter expanded as shown in FIG. 1B. Wire guide 26, which is adaptedto slideably engage a guidewire 30, may be included in distal region 11of the elongate member 10. Alternatively, the wire guide 26 may beintegral with the filter or with both the filter and the elongatemember. In certain embodiments, the wire guide 26 may comprise aring-shaped structure. A cross-sectional view of the elongate member 10through section line C-C is depicted in FIG. 1C. The design andconstruction of a variety of expandable filters suitable for use withinthe filter cartridge system of the present invention is described indetail in Tsugita et al., U.S. Pat. No. 5,910,154.

The filter may be biased to automatically open radially within a bloodvessel. In such filters, the struts of the expansion frame may beconnected to each other at each end and have an intermediate region thatis biased to expand radially as illustrated in FIGS. 1A and 1B. Otherfilters suitable for the present invention are not biased toautomatically open radially within a blood vessel. One embodiment ofsuch a filter, as illustrated in FIG. 6, the struts 28 are notched orotherwise biased to fold out radially. At a distal end of the filter,the struts attach to an inner wire 55 whereas the proximal end of thestruts attach to an outer sheath 55. Proximal displacement of the innerwire 55 with respect to the outer sheath 55 causes the struts to foldout radially, thereby expanding the filter mesh 25 across a blood vessellumen. Alternatively, the filter may be fluid operated as discussedpreviously.

It is to be noted that if the blood filter is biased to automaticallyopen radially within a blood vessel, a restraint is needed to collapsethe filter before it is inserted into a vessel lumen. In one embodiment,a sleeve 5 acts as the restraint to collapse the filter 20 asillustrated in FIG. 1A. To release the restraint, the sleeve 5 may beretracted from the filter 20 by proximally displacing a wire 6 asillustrated in FIG. 1B.

To deploy the cartridge filter system of the present invention, the wireguide 26 engages the guidewire 30 having a proximal end and distal end33. The guidewire 30 is slideably received by elongate member 10 throughwire guide 26 as depicted, for example, in FIG. 1D. Differentconstructions of the distal end 33 of the guidewire 30 are depicted inFIGS. 2A, 2B, and 2C. Distal end 33 may assume a substantially linearconfiguration relative to the proximal end of the guidewire as depictedin FIG. 2A. Alternatively, distal end 33 may assume an angularconfiguration relative to the proximal end of the guidewire as depictedin FIG. 2A. Distal end 33 may be shaped like a fishhook as depicted inFIG. 2C. The distal region of the guidewire may be constructed of aflexible material to facilitate entry through a region of interest, andpreferably is equipped with an atraumatic tip as is known in the art.The embodiments in FIGS. 2B and 2C, having a curvilinear design, areparticularly useful in achieving access to a complex lesion in atortuous vessel.

FIGS. 3A and 3B depict alternative embodiments of expandable filter 20mounted on the distal region of elongate member 10. In FIG. 3A, thefilter 20 comprises an expansion frame 22 that is parachute-shaped andmesh 25 that is welded or adhesive bonded to struts 28 of the expansionframe 22. Wire guide 26 is included in the distal region of the elongatemember and projects distally from filter 20 for engaging a guidewire. InFIG. 3B, filter 20 comprises an expansion frame 22 that assumes theshape of an eggbeater in its expanded state and wherein struts 28 arecompressible.

By way of example, when the cartridge filter system as disclosed hereinis intended for use in the aorta, the area of the mesh 25 required forthe device is calculated from Bernoulli's equation as described in ourearlier applications including Barbut et al., U.S. Pat. No. 5,662,671,Barbut et al., U.S. application Ser. No. 08/553,137, filed Nov. 7, 1995,Barbut et al., U.S. application Ser. No. 08/580,223, filed Dec. 28,1995, Barbut et al., U.S. application Ser. No. 08/584,759, filed Jan. 9,1996, Barbut et al., U.S. application Ser. No. 08/640,015, filed Apr.30, 1996, and Barbut et al., and U.S. application Ser. No. 08/645,762,filed May 14, 1996.

The guidewire and slideable filter disclosed herein may be used in thecarotid arteries, the coronary arteries, the aorta, and in wheretemporary filtration is desired. In an embodiment of the cartridgefilter system that is to be used in the aorta, the filter material is amesh 25 with dimensions within the following ranges is desirable: mesharea is 0.004-5 in.sup.2, more preferably 0.007-4 in.sup.2, morepreferably 0.010-3 in.sup.2, more preferably 0.015-2 in.sup.2, morepreferably 0.020-1 in.sup.2, more preferably 0.025-0.076 in.sup.2; meshthickness is 60-280 .mu.m, more preferably 70-270 .mu.m, more preferably80-260 .mu.m, more preferably 90-250 .mu.m, more preferably 100-250.mu.m, more preferably 120-230 .mu.m, more preferably 140-210 .mu.m;thread diameter is 30-145 .mu.m, more preferably 40-135 .mu.m, morepreferably 50-125 .mu.m, more preferably 60-115 .mu.m, more preferably70-105 .mu.m, and pore size is 500 .mu.m or less, more preferably 400.mu.m or less, more preferably 3300 .mu.m or less, more preferably 200.mu.m or less, more preferably 100 .mu.m or less, more preferably 50.mu.m or less and usually larger than at least a red blood cell. In apreferred embodiment of the invention, mesh area is 2-8 in.sup.2, meshthickness is 60-200 .mu.m, thread diameter is 30-10 .mu.m, and pore sizeis 5-300 .mu.m. In a further preferred embodiment of the invention, mesharea is 3-5 in.sup.2, mesh thickness is 60-150 .mu.m, thread diameter is50-80 .mu.m, and pore size is 100-250 .mu.m.

In other embodiments, the filter material comprises a thin film lasercut with holes to allow blood flow (not illustrated). Typical dimensionsinclude pore size of 20-500 .mu.m, a thickness of 0.0005-0.003 inches,and area approximately same as for meshes described above.

Once appropriate physical characteristics are determined, suitable mesh25 can be found among standard meshes known in the art. For example,polyester meshes may be used, such as meshes made by Saati Corporationsand Tetko Inc. These are available in sheet form and can be easily cutand formed into a desired shape. In a preferred embodiment, the mesh iswelded (e.g., sonic or laser) or sewn into a cone shape. Other meshesknown in the art, which have the desired physical characteristics, arealso suitable. Anticoagulants, such as heparin and heparinoids, may beapplied to the mesh to reduce the chances of blood clotting on the mesh.Anticoagulants other than heparinoids also may be used, e.g., ReoPro(Centocor). The anticoagulant may be painted or sprayed onto the mesh. Achemical dip comprising the anticoagulant also may be used. Othermethods known in the art for applying chemicals to mesh may be used.

The length of the guidewire 30 and the elongate member 10 will generallybe between 30 and 300 centimeters, preferably approximately between 50and 195 centimeters. The filter will be capable of expanding to an outerdiameter of at least 0.2 centimeters, more preferably at least 0.5centimeters, more preferably at least 1.0 centimeters, more preferablyat least 1.5 centimeters, more preferably at least 2.0 centimeters, morepreferably at least 2.5 centimeters, more preferably at least 3.0centimeters, more preferably at least 3.5 centimeters, more preferablyat least 4.0 centimeters, more preferably at least 4.5 centimeters, morepreferably at least 5.0 centimeters. These ranges cover suitablediameters for both pediatric and adult use. The foregoing ranges are setforth solely for the purpose of illustrating typical device dimensions.The actual dimensions of a device constructed according to theprinciples of the present invention may obviously vary outside of thelisted ranges without departing from those basic principles.

In use, as depicted in FIG. 4A, guidewire 30 may be insertedpercutaneously through a peripheral artery or vein and advancedtypically in the direction of blood flow. However, guidewire 30 may beinserted and advanced in a direction opposite the blood flow, e.g.,retrograde through the descending aorta to reach the coronary artery.Distal end 33 of the guidewire 30 is passed through occluding lesion100, typically an theromatous plaque, and positioned distal to theocclusion. Elongate member 10 of FIG. 1A is inserted over the proximalend of guidewire 30 through wire guide 26, and advanced distally untilfilter 20 is positioned distal to plaque 100 as depicted in FIG. 4B. Byhaving wire guide 26 engage the guidewire 30, the filter 20 and theelongate member 10 can be easily steered intravascularly to reach theregion of interest. Filter 20 is expanded to capture embolic material,such as calcium, thrombi, plaque, and/or tissue debris. The useful invivo life of filter 20 depends greatly on the type of medical procedurebeing performed, the condition of the patient (such as whether thepatient is receiving an anticoagulant), and volume of blood flow.Although current filters can be deployed for relatively long periods(upwards of 60 minutes), it is possible that current filters will haveshorter useful in vivo deployment times for the reasons noted above.Should the useful in vivo life of filter 20 be exceeded, filter 20 mustbe replaced by an unused filter. Unlike prior art systems in which thefilter was integrated with the guidewire, in the present invention,filter 20 and elongate member 10 may be retracted from the body andguidewire 30 without requiring the removal of guidewire 30. An unusedfilter 20 and elongate member 10 may then be inserted over the proximalend of guidewire 30 through a wire guide 26, and advanced distally untilfilter 20 is positioned distal to plaque 100 similarly as depicted inFIG. 4B.

As illustrated in FIG. 4B, the wire guide 26 may engage the guidewire 30at a single discrete location. Suitable wire guides 26 that engage theguidewire at a discrete location may comprise, for example, a ring orsimilar structure. Such embodiments of the cartridge filter system maybe denoted “partially-threaded” or monorail systems because, proximal tothe wire guide 26, the guidewire 30 and the elongate member 10 areseparate and independent from one another. Other medical devices havingmonorail construction are known in the art. Note that proximal to thewire guide, a clinician must contend with two separate and independentstructures within the vessel lumen. This can make the insertion ofadditional therapy devices into the vessel lumen difficult. For example,a therapy device, such as an angioplasty balloon, will typically engagethe guidewire to assist positioning the therapy device in the vessel. Asthe therapy device is displaced along the guidewire, it may cause theelongate member to injure the vessel lumen.

To prevent such injury, the filter and elongate member may be releasablyattached through an interlock in a monorail embodiment of the invention.As illustrated in FIG. 4C, the interlock may comprise a mechanicalinterlock having a threaded portion 9 at the distal end of the elongatemember 10 adapted to engage a threaded portion 8 attached to the filter20. After the filter 20 has been expanded to cover the vessel lumen, theelongate member 10 is rotated to release the mechanical interlock byunthreading the threaded portions 8 and 9. Note that the filter 20 isthen retained only by the guidewire 30. To assist the retention of thefilter 20 along the guidewire, the guidewire may have a stop 60 toprevent further distal displacement of the filter. In such anembodiment, the filter is free, however, to displace proximally. Thepressure from the blood flow and the tension provided by the expansionof the filter against the walls of the vessel lumen will tend to preventproximal displacement. Although such forces will tend to preventproximal displacement, it may be beneficial during some procedures toallow a small amount of proximal displacement when necessary.

As used herein, “elongate member” denotes any structure suitable foradvancing filter 20 into position within a vessel while engagingguidewire 30 through a wire guide 6. Thus elongate member 10 maycomprise, of course, a wire. Alternatively, elongate member 10 maycomprise a catheter such as a balloon catheter suitable for angioplasty.If elongate member 10 comprises a catheter, the lumen of the cathetermay serve as the wire guide 26. In such an embodiment, elongate member10 slideably engages guidewire 30 in an “over-the-wire” manner similarto, for example, the manner in which a single lumen catheter is threadedover a guidewire in neuroradiological procedures. Turning now to FIG.4D, an over-the-wire cartridge filter system is illustrated. Elongatemember 10 comprises a catheter or sleeve 35 wherein the lumen 40 of thecatheter 35 serves as the wire guide 26. The expansion frame 22 offilter 20 attaches to the catheter 35 along the catheter wall portion42. Unlike the monorail system illustrated in FIG. 4B, a clinicianthreading additional devices into the blood vessel in which anover-the-wire cartridge filter system is deployed will not have tocontend with two independent structures within the blood vessel lumen.Inspection of the monorail cartridge filter system illustrated in FIG.4B reveals that proximal to the filter 20, the guidewire 30 and elongatemember 10 are independent of one another, potentially hampering thedeployment of additional devices within the blood vessel. Nevertheless,monorail or partially-threaded systems possess advantages over anover-the-wire system (that may be denoted as “filly-threaded”). Forexample, in angioplasty procedures or the like, the guidewire 30 must berelatively long to extend from vessels within a patient's leg to theheart. If the proximal portion of the guidewire 30 that extends outsidethe patient's body is relatively short, there comes a point at which, asthe elongate member 10 is retracted from the body, the elongate member10 will entirely cover this external proximal portion of the guidewire30 (in an over-the-wire cartridge filter system). The clinician wouldthen no longer be able to maintain the position of the guidewire 30.Thus, as is known in other medical procedures, over-the-wire medicaldevices require relatively long proximal transfer portions external to apatient's body, causing inconvenience during catheterization procedures.

The present invention includes over-the-wire filter cartridge systemembodiments that do not require the relatively long proximal transferportions of prior art over-the-wire systems. For example, in FIGS. 5Aand 5B, an embodiment of such a filter cartridge system is illustrated.Elongate member 10 may include a ring-shaped wire guide 26 that attachesto the expansion frame 22 of filter 20 (filter 20 only partlyillustrated). Elongate member 10 also includes a body portion 46 havinga longitudinally extending groove 45 adapted to slideably engage wireguide 30. In one embodiment, groove 45 is shaped such that body portion46 has a C-shaped cross section as illustrated in FIG. 5B. The elongatemember 10 is constructed of a suitably flexible material such that aclinician may force guidewire 30 into the groove 46 by forcing apartarms 47 and 48 of the “C” formed by groove 46. The guidewire 30 wouldthen be held within groove 46 by arms 47 and 48. Outside the body, theelongate member 10 and the guidewire 30 may be kept separate,eliminating the need for a long proximal transfer portion outside thepatient's body. Within a vessel, however, the system of FIGS. 5A and 5Bwill operate as an over-the-wire system. As the filter 20 and elongatemember 10 are retracted from the guidewire 30 and the patient's body,the guidewire 30 may be separated from the elongate member 10 by pullingapart the already separated portions of elongate member 10 and guidewire30. The resulting tension flexes arms 47 and 48 outwardly, allowing theguidewire 30 to be removed from the groove 45.

Although the groove 45 slideably engages the guidewire 30, it is to benoted that (particularly when body portion 46 has a C-shaped crosssection) the guidewire 30 may not be entirely circumferentiallysurrounded by elongate member 10 as is the case in ordinaryover-the-wire systems (such as illustrated in FIG. 4 c). To provide fillcircumferential support around guidewire 30, elongate member 10 may haveone or more spiral portions 47 wherein the elongate member spirals aboutguidewire 30 such that spiral portion 47 resembles coils of a spring.Note that should the elongate member 10 include the spiral portions 47,as the filter 20 and elongate member 10 are retracted from the guidewire30, the clinician will unravel the spring portion 47 to separate it fromthe guidewire 30. Conversely, as the elongate member 10 is beingadvanced along guidewire 30, the clinician must ravel spiral portion 47about the guidewire 30 to continue deployment of a filter.

Regardless of whether the cartridge system is an over-the-wire or amonorail system, one of ordinary skill in the art will appreciate thatthere are a number of ways to actuate the filter of the presentinvention. For example, if the filter is biased to automatically openradially within a blood vessel, the cartridge filter system may becontained within a catheter or sheath 5 as illustrated in FIG. 1A. Asthe elongate member and filter are advanced beyond the sheath 5, thefilter will automatically expand radially within the vessel because ofthe pre-existing bias within the filter as illustrated in FIG. 1B.Alternatively, the filter may be fluid operated wherein the filtercontains a balloon that expands to expand the filter. In addition, thefilter may be mechanically actuated by the clinician.

Turning now to FIG. 6, a mechanically actuated cartridge filter systemis illustrated. In such filters, the elongate member 10 may comprise asheath or catheter 50 containing an inner wire 55 wherein the expansionframe 22 includes a plurality of struts 28 attached to the distal end ofthe sheath 50. The struts 28 extend distally from the sheath 50 andattach to the distal end of the inner wire 55 that is distally exposedbeyond the sheath. At an intermediate region, the struts 28 are notchedor otherwise biased to fold out radially. Filter mesh 25 is attached tothe struts 28 between the intermediate region and the distal end of theinner sheath 55. To open the filter 20, the sheath 50 is fixed inposition, and the inner wire 55 is proximally displaced, compressing thestruts 28 and causing them to bend or buckle at the intermediate regionand move radially outwardly, expanding the filter mesh 25 across theblood vessel. It is to be noted that the guidewire 30 may have a stop 60formed to assist the positioning and deployment of the filter 20 alongthe guidewire 30.

As used herein, “inner wire” means any structure suitable to beslideably disposed within the sheath 50 and stiff enough to compress thestruts 28 as the inner wire 55 is proximally displaced with respect tothe sheath 50. Thus, as illustrated in FIG. 6, the inner wire 55 maycomprise an inner sheath 55 that slideably contains the guidewire 30within a lumen of the inner sheath. Note that the inner sheath 55 andthe sheath 50 may each possess a body portion having a longitudinallyextending slit therein (not illustrated). Within both the inner sheath55 and the sheath 50, the combination of the slit and the lumen wouldtherefore comprise the longitudinally extending groove alreadydescribed. Therefore, the cartridge filter system illustrated in FIG. 6could be advanced within a blood vessel in an over-the-wire fashion yetnot require a relatively long proximal transfer portion as describedwith respect to the embodiment of the cartridge filter systemillustrated in FIGS. 5A and 5B.

Another method for deploying a slideable filter along a guidewire isshown in FIGS. 7A-7D. According to this method, guidewire 30 is firstpositioned across lesion 100 within vessel 101. Guidewire 30 may includea distal stop 102. Filter 110, having proximal end 111 and distal end112, is then advanced along guidewire 30. This step of advancement istypically performed with capture sheath 105 disposed about filter 110.Advancement may also be accomplished using an advancing mechanism 120having distal end 121 that bears against proximal end 111 of filter 110.Alternatively, the static friction between filter 110 and sheath 105 maybe adequate to advance the filter along guidewire 30, in which casesheath 105 is the advancing mechanism. Once filter 110 is positioneddownstream of lesion 100, capture sheath 105 is withdrawn, allowing thefilter to expand as depicted in FIG. 7C. Further distal advancement offilter 110 is prohibited by frictional engagement of filter 110 by thevessel lumen or by stop 102 when present. Alternatively, filter 110 maybe equipped with an actuatable locking mechanism that engages guidewire30 when the filter is properly positioned. After expansion of filter110, capture sheath 105 and advancing mechanism 120 are withdrawn fromthe region of interest as shown in FIG. 7D, and removed from thepatient's vessel.

In certain embodiments, the advancing mechanism bears against proximalend 111 of filter 110, but is not otherwise connected. In otherembodiments as shown in FIG. 8, advancing mechanism 125, having distalend 126, is coupled through flush contact interlock 127 to proximal end111 of filter 110. In this case, the interlock is activated by magneticor electromagnetic force and is releasable. FIGS. 9A and 9B show analternative mechanical interlock. In FIG. 9A, pivoting claws 130 aremounted at the distal end of advancing mechanism 125. The distal end ofeach claw 130 is adapted to engage recess 131 disposed circumferentiallyabout proximal end 111 of filter 110. Claws 130 are maintained incontact with recess 131 by the action of locking sheath 133 that bearscircumferentially against claws 130. When capture sheath 105 and lockingsheath 133 are withdrawn as depicted in FIG. 9B, claws 130 pivot out ofengagement, thereby releasing filter 110.

Another mechanical interlock is shown in FIGS. 10A and 10B. FIG. 10Ashows a threaded interlock between threaded screw 136 mounted onproximal end 111 of filter 110. The screw engages coupling 135 having athreaded portion adapted to receive screw 136. FIG. 10B depictsdisengagement of coupling 135 from screw 136 to permit removal ofadvancing mechanism 125 and capture sheath 105 from the patient'svessel. In order to disengage the coupling from the screw it may benecessary to have a rotational lock on the filter, so that the couplingcan be rotated while the filter remains fixed.

A further mechanical interlock is shown in FIGS. 11A-11D. FIG. 11A showsfirst hook 140 mounted at the distal end of advancing mechanism 125.Second hook 141 is mounted at proximal end 111 of filter 110, and isadapted to engage first hook 140. Engagement of hooks 140 and 141 isdependent upon proper rotational alignment of the hooks. This alignmentis maintained so long as sheath 105 surrounds the interlock. FIG. 11Bshows the interlock after placement within a vessel and removal ofsheath 105. As depicted in FIG. 11C rotation of hook 140 disengages theinterlock. Advancing mechanism 125 and sheath 105 are then removed fromthe region of interest and from the patient's vessel as shown in FIG.11D. In addition to the detachable interlock mechanisms discussed above,a number of additional mechanisms have been disclosed in U.S. Pat. Nos.5,312,415, 5,108,407, 5,891,130, 5,250,071, 5,925,059, 5,800,455,5,800,543, 5,725,546, 5,350,397, 5,690,671, 5,944,733, 5,814,062, and5,669,905, all of which are expressly incorporated herein by referencein their entirety. It will understood that any of the interlocksdisclosed in any of these patents may be used in the present invention.

As noted above, one or more distal and/or proximal stops may be placedalong the guidewire. These stops may be pre-mounted, installed during aprocedure, or integral with the filter and simultaneously insertedtherewith. An actuatable stop is shown in FIGS. 12A-12E. Referring toFIG. 12A, the proximal stop is comprised of off-centered tubes, shownhere as first tube 145, second tube 146, and biasing element 147connecting the first and second tubes. When misaligned as shown in FIG.12A, first and second tubes 145 and 146, respectively, pinch andfrictionally engage guidewire 30 as shown in FIG. 12B. In use, thisslideable stop can be employed proximal of the filter as shown in FIG.12C. Sheath 105 contains advancing mechanism 125, an actuatable stopincluding first and second tubes 145 and 146 coupled through biasingelement 147, and filter 110. Sheath 105 forces first and second tubes145 and 146 into near coaxial alignment, thereby permitting the stop toslide over guidewire 30. This assembly is advanced across lesion 100until the filter reaches optional distal stop 102. The filter andproximal stop are then released from sheath 105 as depicted in FIG. 12D,the stop engaging the guidewire. Sheath 105 and advancing mechanism 125are then removed from the patient's vessel. After performance of anendoluminal procedure (e.g., angioplasty, stent deployment, angiography,atherectomy), the filter and stop are retrieved by sheath 150 asdepicted in FIG. 12E. Sheath 150 first captures first and second tubesof the stop and forces them into alignment against the action of biasingelement 147. In this manner, the stop is de-actuated and again slidesover guidewire 30. Sheath 150 then captures filter 110 that bearsagainst optional stop 102 during advancement of sheath 150 over filter110. The entire assembly, including sheath 150, filter 110, and theproximal stop, are then removed from the patient's vessel.

In another embodiment, a pivoting proximal stop is used as shown inFIGS. 13A-13C. Referring to FIG. 13A, the proximal stop is comprised oftapered proximal section 156 and flat distal section 155, the taperedproximal section allowing a filter to pass distally when advanced overthe stops Proximal section 156 has lumen 157 adapted to receiveguidewire 30. Section 155 lies in a plane substantially perpendicular tothe axis of lumen 157. In this manner, the proximal stop pivots andfrictionally engages guidewire 30 when proximal end 111 of filter 110bears against section 155. Filter 110 is retrieved and withdrawn overthe stop as shown in FIG. 13B. Sheath 105, optionally a stepped sheathas depicted in FIG. 15B, aligns the stop with the opening at theproximal end 111 of filter 110, permitting the filter to pass proximallyover the stop as shown in FIG. 13C.

In another embodiment, a slip stop is used as the proximal stop asdepicted in FIGS. 14A and 14B. Slip stop 160 comprises a tubular segmenthaving open distal end 162 and tapered proximal end 161. Guidewire 30passes smoothly through proximal end 161 when distal end 162 is centeredabout guidewire 30. However, when stop 160 becomes misaligned, as shownin FIG. 14A, proximal end 161 pinches and frictionally engages guidewire30, preventing proximal advancement of filter 110. To retrieve filter110, sheath 105, optionally a stepped sheath as shown, is advanceddistally over stop 160 and filter 110, thereby aligning slip stop 160with the opening at proximal end 111 of filter 110, as shown in FIG.14B.

FIG. 15A shows a guidewire having one distal stop 102. FIG. 15B shows aguidewire having distal stop 102 and proximal stop 165. Proximal stop165 may be mounted on a pivot about its mid-point, thereby allowing afilter to pass proximal to distal, and later be retrieved distal toproximal, provided sufficient force is applied to pivot the stop. FIG.15C shows two proximal stops 166 and 167, each comprising a plurality ofpivoting cleats 168 attached to housing 169 that engages guidewire 30.It will understood that any number of proximal and distal stops may beemployed, including 1, 2, 3, 4, 5, 6, 7, or any other desired numberdepending on the procedure. FIG. 15D shows retrieval of filter 110.Sheath 105 restrains cleats 168 to allow passage of proximal end 111 offilter 10 over the cleats. In certain embodiments, it may desirable forsheath 105 to include a sharp step, shown as numeral 170 in FIG. 15E.This sheath will maintain closure of cleats 168 until the cleats areguided within proximal end 111 of filter 110, permitting removal of thefilter over the cleats.

The sliding filter as disclosed herein may be constructed with an opencarriage as shown in FIG. 16A or a continuous carriage as shown in FIG.16B. Referring to FIG. 16A, a plurality of struts 181 join proximal end111 to distal end 112. Filter 110 is disposed about a portion of struts181, either over or under the struts. Struts 181 buckle radially outwardwhen proximal end 111 and distal end 112 are forced together. In certainembodiments, distal end 112 will include a tapered edge as shown in FIG.16A. FIG. 16B depicts a continuous carriage extending from proximal end111 to distal end 112, and terminating in a tapered distal edge. Slidingring 180 may be incorporated distal or proximal. Struts 181 areconnected at a first end to carriage 182 and at a second end to slidingring 180. Struts 181 buckle radially outward when sliding ring 180 andcarriage 182 are forced together.

Although the foregoing invention has, for the purposes of clarity andunderstanding, been described in some detail by way of illustration andexample, it will be obvious that certain changes and modifications maybe practiced that will still fall within the scope of the appendedclaims. Moreover, it will be understood that each and every featuredescribed for any given embodiment or in any reference incorporatedherein, can be combined with any of the other embodiments describedherein.

1. A medical device comprising: an elongate member including a proximal end, a distal end, and a lumen extending therebetween; an expansion frame coupled to the distal end of the elongate member; and a filter mesh disposed over at least a portion of the expansion frame; wherein at least a portion of the elongate member proximal of the expansion frame has a C-shaped transverse cross-section adapted to slidably accept and retain a guidewire inserted laterally into the lumen; wherein at the C-shaped transverse cross-section, the elongate member comprises a first arm and a second arm forming the C-shaped transverse cross-section such that a distance between the first arm and the second arm is less than a maximum diameter of the lumen.
 2. The medical device of claim 1 wherein the elongate member includes a longitudinal groove extending along at least a portion of a length of the elongate member.
 3. The medical device of claim 2 wherein the longitudinal groove is configured to expand and receive a guidewire within a portion of the lumen.
 4. The medical device of claim 3 wherein the elongate member includes a flexible material.
 5. The medical device of claim 3 further comprising one or more springs configured to be disposed about at least a portion of the elongate member, wherein the one or more springs are configured to restrict a portion of the elongate member from expanding.
 6. The medical device of claim 5 wherein the one or more springs are provided proximal of the distal end of the elongate member.
 7. The medical guidewire of claim 2 wherein at least a portion of the elongate member has a C-shaped transverse cross-section wherein the width of the groove is less than the diameter of a guidewire slidably retained within the lumen thereof.
 8. The medical device of claim 1 wherein the elongate member is a catheter.
 9. The medical device of claim 1 further comprising a second elongate member including a proximal end, a distal end, and a lumen extending therebetween, wherein the second elongate member is slidably disposed within at least a portion of the lumen of the elongate member.
 10. The medical device of claim 9 wherein at least a portion of the filter mesh is attached to a portion of the second elongate member.
 11. The medical device of claim 10 wherein the portion of the filter mesh that is attached to the second elongate member is attached to the distal end of the second elongate member.
 12. The medical device of claim 9 wherein the lumen of the second elongate member is adapted to slidably receive a guidewire therein.
 13. The medical device of claim 9 further comprising a stop disposed on a guidewire distal of the distal end of the second elongate member, wherein the stop is configured to engage the distal end of the second elongate member to prevent distal movement of the second elongate member relative to the guidewire.
 14. A medical device comprising: a guidewire; an elongate member including a proximal end, a distal end, and a lumen extending therebetween, wherein the elongate member includes a longitudinal groove extending at least a portion of the length of the elongate member, the longitudinal groove having an unexpanded width; an expansion frame coupled to the distal end of the elongate member; and a filter disposed over at least a portion of the expansion frame; wherein the longitudinal groove is configured to expand and receive the guidewire inserted laterally into the lumen through the groove; wherein the unexpanded width of the longitudinal groove is less than a diameter of the guidewire.
 15. The medical device of claim 14 further comprising one or more springs configured to be disposed about at least a portion of the elongate member, wherein the one or more springs are configured to restrict a portion of the elongate member from expanding.
 16. The medical guidewire of claim 14 wherein at least a portion of the elongate member has a C-shaped cross-section. 